In the prior art, numerous different gas turbine components are known which have the film-cooling openings described in the introduction. For example, WO 2013/188645 discloses a turbine blade having film-cooling openings, the diffuser-like region of which transitions into two vane regions which are separated by a rib. The film-cooling openings are used in a known manner with the aim of preventing premature damage to the material or to the gas turbine component, in order that the predetermined service life is attained. In detail, it is sought by means of the film-cooling openings to provide an areal cooling film over the surface of the gas turbine component in order, during operation, to protect the surface against the damaging influences of the hot gas flowing along it. The cooling air required for forming the cooling film must however be provided. Said cooling air is often extracted from the cycle of the gas turbine, such that the extracted fraction cannot participate in the generation of energy. This reduces the efficiency of the gas turbine, such that there is likewise a desire to keep the cooling-air flow rate as low as possible. Furthermore, there is a need to keep the number of film-cooling holes low, which leads not only to a saving of cooling air but also to a gas turbine component which is easier to produce and less expensive.
An alternative arrangement to this is known from the publication US 2013/0205803 A1. In said document, it is proposed that the widening film-cooling holes of a row make contact with one another. Here, the diffuser regions make contact along an edge, which diffuser regions in turn end at the downstream transverse edges of the adjacent diffusers. This creates a gapless row of closely successive corners with interposed rectilinear diffuser outlet edges, which can weaken the blade material.
It is also known for such film-cooling holes to be used not only for the areal cooling of the gas turbine component but also for the cooling of a so-called rubbing edge which is arranged at the free end of a turbine rotor blade and which is moved relative to a static housing wall of the flow path of the gas turbine. Such rubbing edges are likewise exposed to the hot gas influences, wherein, owing to their exposed position—they generally project perpendicularly in free-standing fashion from a turbine blade wall surface oriented approximately parallel to the flow-path delimitation of the gas turbine—said rubbing edges are, however, relatively difficult to cool.
In particular, in the prior art, an effect is noticeable whereby it is only with increasing distance from the film-cooling opening that the individual cooling-air filaments formed up to that point merge to form an areal cooling film. However, owing to the internal cooling-duct structure of the turbine blade and the thus predefined position of the film-cooling holes provided for the cooling of the rubbing edge, said film-cooling holes have hitherto been arranged too close to the rubbing edge to form a gapless cooling film. Consequently, viewed locally, hot-gas filaments arose in between the individual cooling-air filaments before the merging of the latter, which hot-gas filaments were able to cause local damage to the rubbing edge.
For this reason, it is desirable, in particular for rows of film-cooling openings used for the cooling of rubbing edges, for areally continuous cooling along the film-cooling row to be achieved as close as possible downstream of the film-cooling openings.